Imagine a number of operative units, which via communication radio are in connection with a guidance central. The operative units can be vehicles, airplanes or vessels giving reports concerning their positions, arrived activities etc. The reports constitute the base for the actions, which are ordered from the guidance central. In the guidance central must exist a "memory" about what has been reported, at least during a restricted time. This is usually effected by means of a sort of notations. It is however evident, that the problems in connections herewith are growing with the number of the operative units, which are to be guided from the guidance central.
For the operative units the problem is, to send the reports as quickly and uncomplicated as possible. It ought to be observed that reporting often must be done when "something happens" i.e. in a hurry.